WO2018037700A1 - Detection light generation element and detection light irradiation method - Google Patents

Abstract

A detection light generation element 1 is provided with: an optical waveguide 4; a grating section 5A configured from grooves periodically formed in the optical waveguide 4; and a cladding section 3, which is in contact with the optical waveguide 4, and is formed of a material having a refractive index that is lower than that of the material of the optical waveguide 4. Propagation light propagating in the optical waveguide 4 is diffracted by means of the grating section 5A, and the propagation light is outputted to a plurality of different directions as diffracted light A1-A5.

Description

Detection light generating element and detection light irradiation method

The present invention relates to a detection light generating element for obtaining information by emitting detection light in a plurality of different directions.

Demand for high-definition, high-image-quality, large-screen displays and projectors is increasing due to the progress of multimedia and digital signage, and the development of optical scanning elements that scan laser light at a wide angle has been activated. Recently, optical scanning elements can be used as laser radars, laser scanners, and LiDAR (Light Detection and Ranging), and can be used for obstacle detection systems and ranging systems for automatic driving control of automobiles and position control of robots and drones. The application of is being considered.

These optical scanning (scanning) mechanisms are mainly mechanical methods such as a polygon mirror method and a MEMS mirror method.

Patent Documents 1 and 2 are mechanical systems that scan a laser beam on a motor-driven mirror. The motor-driven mirror is rotated to scan the laser beam. Reflected light from the object is detected by a light receiving element, and the distance and position from the object are determined from the time delay. As the mirror, a plane mirror or a polygonal polygon mirror is used.

Patent Document 3 is a mechanical system using a MEMS mirror. The structure of the MEMS is that a movable part is formed on a silicon by a beam having a biaxial degree of freedom using a semiconductor process, and a highly reflective metal reflective film is formed on the surface of the movable part. It is a mirror. A permanent magnet is arranged around the operating part, and a Lorentz force is generated by passing a current through the coil of the movable part to control the emission direction.

In the light receiving element division method described in Patent Document 4, no operating part is required. This realizes detection of the measured surface body by widening the laser beam with a lens and detecting the reflected light with the divided light receiving elements. However, if the number of divisions is increased, the amount of reflected light incident on one light receiving element is reduced, resulting in a poor signal noise (S / N) ratio. In this case, there is a concept of increasing the power of the light source in order to increase the amount of received light, but the cost of the light source is increased due to the high power of the light source, and an eye-safety problem arises.

On the other hand, the present inventor proposed an optical switching element by using a lithium niobate or lithium tantalate substrate, forming a plurality of prism-like domain-inverted portions on the substrate, further thinning the substrate, and forming electrodes. did. However, this is not an optical scanning element for scanning at a wide angle because the direction displacement of the emitted light by the electro-optic effect is 10 ° or less.

Also, in the case of an element using the electro-optic effect, it is well known that an electrode is formed on a prism (Non-Patent Document 1).

However, a prism deflector using an electro-optic crystal such as lithium niobate has a relatively small change in refractive index due to the electro-optic effect. For example, in the case of lithium niobate, in order to obtain a refractive index change Δn = 0.001, it is necessary to apply a large electric field of about 4.5 kV / mm to the crystal.

For this reason, Patent Document 6 discloses a structure in which the thickness of the lithium niobate substrate is reduced in order to reduce the driving voltage.

Patent Document 7 is an example of a switching element to which a grating is applied, and includes a slab type optical waveguide, a grating part, and an electrode formed on the upper part of the grating part. In this case, one grating portion is long and formed along the traveling side of the slab waveguide, and is periodically configured in a direction perpendicular to the traveling direction of the slab waveguide. The light propagating through the slab waveguide functions as a diffraction grating because the grating portion has a periodic refractive index structure when a voltage is applied. It utilizes the fact that light is deflected by the diffraction effect. In this case, the deflection angle is 2-3 °.

Scrymgeour, D.A., ”Large-angle electro-optic laserscanner on LiTaO3 fabricated by in situ monitoring of ferroelectric-domainmicropatterning, Appl. Opt., 40-34, (2001)

Patent 5802659 JP2013-148446 JP2013-003253 Patent 5683629 JP2013-195687 JP2011-48067 Patent 5793308

However, the conventional optical scanning element has a problem that a movable part is required or a signal / noise ratio in the light receiving element is increased. An optical switching element using a prism-shaped domain inversion unit is known, but this deflects the direction of propagating light by about 10 ° or less, and is not suitable as a laser scanner.

An object of the present invention is to provide a detection light generating element that does not require a movable part, generates detection light at a wide angle without scanning light, and can emit a wide range of angles.

The present invention
A detection light generating element for irradiating the measurement surface with detection light,
Optical waveguide,
A grating portion formed of grooves and protrusions periodically formed in the optical waveguide, and a cladding portion that is in contact with the optical waveguide and made of a material having a refractive index lower than that of the material of the optical waveguide,
The propagating light propagating through the optical waveguide is diffracted by the grating section, and the diffracted light generated from the grating section is emitted as a plurality of different directions as the detection light.

Further, the present invention is a method of irradiating a surface to be measured using the detection light generating element,
The detection light emitted from the detection light generation element is irradiated onto the surface to be measured, and data relating to the surface to be measured is obtained using reflected light from the surface to be measured.

According to the present invention, a diffraction grating including a grating portion is provided in an optical waveguide, and light can be emitted to the outside of the optical waveguide in a direction (direction different from the optical waveguide surface) determined by the period of the diffraction grating. . In addition, since the emission direction changes for each wavelength, the light can be diffused over a wide range of angles as a whole.

Furthermore, by providing diffraction gratings with different periods, the detection light generating elements that emit light at a wider range of angles can be realized by adding the ranges irradiated by the respective diffraction gratings. Can be obtained.

For example, by irradiating light at a wide angle, it is possible to obtain three-dimensional information by measuring the time until the light incident on the object is reflected and returned, and the obstacle can be obtained. Can be detected.

It is a schematic diagram which shows the detection light generation element 1 which concerns on embodiment of this invention. It is sectional drawing which shows typically the detection light generation element 1A which concerns on other embodiment. It is a perspective view which shows typically the detection light generating element 1A which concerns on other embodiment. It is a schematic diagram which shows the beam of the emitted light radiate | emitted from a grating part. It is a schematic diagram which shows the relationship between the incident light and emitted light in a Bragg grating coupler. It is a graph which shows the relationship between a grating period and the radiation angle of emitted light. It is a graph which shows the relationship between a grating period and the radiation angle of emitted light. A state in which light emitted from the detection light generating element is reflected and received by the divided light receiving elements 25 is shown. A state in which the surface to be measured is scanned while the detection light generating element is moved in the X direction and the Y direction and light is received by the divided light receiving elements is shown. The state which scans an object surface using the detection light generating element of this invention is shown. The state which scans an object surface using the detection light generating element of this invention is shown. (A), (b), (c) is a cross-sectional view schematically showing the cross-sectional structure of each detection light generating element. (A), (b), (c) is a cross-sectional view schematically showing the cross-sectional structure of each detection light generating element. (A), (b) is a cross-sectional view which each shows typically the cross-section of each detection light generation element.

FIG. 1 is a perspective view schematically showing a detection light generating element 1 according to an embodiment of the present invention.
In this example, the optical waveguide 4 is formed on the support substrate 2 via the clad layer 3, and the optical waveguide 4 constitutes a slab type optical waveguide. An upper cladding layer (not shown) can be provided on the upper surface 4 c of the optical waveguide 4. The optical waveguide 4 is provided with a light incident surface 4a and a facing surface 4b facing the incident surface 4a. The optical waveguide 4 is provided with a diffraction grating 5A formed by grating grooves having a constant period.

In operation, light is incident as indicated by an arrow I from the incident surface 4a of the optical waveguide. This light propagates in the optical waveguide 4, and the optical waveguide functions as a slab type optical waveguide. The grating portion 5A functions as a diffraction grating. As a result, as will be described later, diffracted light is emitted outside the element by the action of the diffraction grating. In this example, first-order diffracted light A1, second-order diffracted light A2, third-order diffracted light A3, fourth-order diffracted light A4, and fifth-order diffracted light A5 are emitted from the grating portion 5A. Since each diffracted light is emitted in a different direction, detection light can be generated in a wide range at the same time.

In the example of FIG. 1, a single grating portion is used, and first-order diffracted light and higher-order diffracted light are emitted. However, in the example of FIGS. 2 and 3, a plurality of grating portions are provided, and diffracted light of a plurality of orders is emitted from each grating portion.

In this example, the optical material layer 14 is formed on the support substrate 2 via the clad layer 3, and the elongated ridge type optical waveguide 6 is provided on the upper surface 14 a side of the optical material layer 14. An upper cladding layer (not shown) can be provided on the upper surface 14 a of the optical material layer 14. The optical waveguide 6 is provided with a light incident surface 6a and a facing surface 6b facing the incident surface 6a. The optical waveguide 6 is provided with grating portions 5B, 5C, 5D, and 5E in the longitudinal direction.

During operation, light is incident as indicated by an arrow I from the incident surface 6 a of the optical waveguide 6. This light propagates in the optical waveguide 6. Here, when the grating portions 5B to 5E having a plurality of different periods are formed, each grating portion functions as a diffraction grating. As a result, as will be described later, each diffracted light is emitted in different directions by the action of each diffraction grating. Furthermore, diffracted lights having different orders are radiated from the respective grating portions in different directions.

That is, in this example, the first-order diffracted light B1 is emitted from the grating portion 5B, the first-order diffracted light C1 and the second-order diffracted light C2 are emitted from the grating portion 5C, and the first-order diffracted light D1, Next-order diffracted light D2 and third-order diffracted light D3 are emitted, and first-order diffracted light E1, second-order diffracted light E2, and third-order diffracted light E3 are emitted from the grating portion 5E. The directions of the first-order diffracted light radiated from each grating part are different from each other, and the directions of the diffracted light having different orders radiated from the same grating part are also different from each other. By appropriately selecting these, a wide range can be scanned simultaneously. On the other hand, when the grating period (pitch) is narrow, only the first-order diffracted light can be emitted, and the diffraction order to be used can be determined by the design of this pitch.

FIG. 4 is a schematic diagram for explaining how the outgoing light beam radiated from the grating section spreads.
In this example, it is assumed that the ridge type optical waveguide 6 is formed in the optical material layer 14, and the grating portion 5A is formed therein. The propagating light propagating through the optical waveguide is diffracted by the grating portion and emitted as diffracted light in a predetermined direction. Here, the longitudinal direction of the element is L, and the direction parallel to the grating surface and parallel to the upper surface 6c of the optical waveguide 6 is W. The emitted light is emitted almost in the W direction. As a result, as shown by E, outgoing light is radiated from the grating portion toward a wide range. On the other hand, the angle (radiation angle) θa of the emitted light with respect to the normal P of the upper surface 6c of the optical waveguide 6 varies depending on the period of the grating portion. As a result, the radiation angle θa can be sequentially changed for a plurality of grating portions.

In the present invention, propagating light is propagated through the optical waveguide, and each grating element functions as a diffraction grating, thereby changing the traveling direction of the propagating light propagating through the optical waveguide and radiating diffracted light from the optical waveguide to the outside. . The principle of this grating coupler will be described.

As shown in FIG. 5, the incident light I incident on the optical waveguides 4 and 6 propagates in the longitudinal direction L with a propagation constant βo, for example. Protrusions 8 and recesses 7 are formed periodically to form a Bragg grating. In the Bragg grating, when the pitch of the periodic structure is Λ, light having a propagation constant that satisfies the phase condition of the following equation (1) propagates.

βq = βo + qK (q = 0, ± 1, ± 2,...) (1)

Here, βo is a propagation constant of the waveguide mode in the waveguide when there is no grating. K = 2π / Λ.

| Βq | <na · k, or | βq | <ns · k
When there is an order q that satisfies the above, it radiates to both the upper side of the optical waveguide and the support substrate side.
Here, na and ns indicate the refractive indexes of the upper cladding 20 and the lower cladding 3 of the optical waveguide core, respectively. K represents the wave number.

The radiation angles θa and θs at this time are determined by the following equation (2).

na · k · sin θa = ns · k · sin θs = βq (2)

(1) The expression (1) can be further expressed by the expression (3). The condition that is actually satisfied is when q ≦ −1. The first-order diffracted light is radiated to the outside of the waveguide at the radiation angles θa and θs calculated when q = −1.

From the above, it can be seen that the radiation angle varies depending on the wavelength. Therefore, by changing the period of the grating part, the emission angles θa and θs of the emitted light emitted from each grating part can be changed.

Also, equations (1) and (3) hold when q ≦ -1. For this reason, since a part of propagation light is emitted also as high order diffracted light, high order diffracted light can also be used. Here, the higher-order diffracted light means second-order or higher-order diffracted light.

For example, second-order diffracted light is emitted outside the waveguide at radiation angles θa and θs calculated when q = −2, and third-order diffracted light is guided at radiation angles θa and θs calculated when q = −3. The fourth-order diffracted light is radiated to the outside of the waveguide at the radiation angles θa and θs calculated when q = −4. If the order of the diffracted light changes, the radiation angle changes, so there is an advantage that a wide radiation angle can be covered with a small number of grating parts.

However, as the order of the diffracted light increases, the intensity of the diffracted light decreases, so that the distance that can be detected without being able to propagate light far becomes shorter, or the reflected light from the object to be measured even at short distances. There is a problem that the signal intensity is small and the signal / noise ratio (SN ratio) is small. From this viewpoint, the order of the diffracted light is preferably the eighth order or less, and more preferably the fourth order or less.

Hereinafter, the constituent elements of the present invention will be further described.
Optical materials constituting the optical waveguide and the optical material layer are lithium niobate, lithium tantalate, lithium niobate-lithium tantalate, KTP (KTiOPO4), KTN (KTa (1-x) NbxO3), KLN (K3Li2Nb5O15), Glass containing tantalum oxide, alumina oxide, zinc oxide, titanium oxide, magnesium oxide, niobium oxide, silicon nitride, silicon carbide, silicon oxide, or silicon oxide is preferable.

In a preferred embodiment, Tsub / λ is 0.6 or more and 10 or less, where λ is the wavelength of propagating light and Tsub is the thickness of the optical waveguide. If this condition is satisfied, the propagating light propagates through the optical waveguide, so that diffracted light with high resolution can be obtained.

The specific material of the support substrate is not particularly limited, and may be glass such as lithium niobate, lithium tantalate, quartz, quartz, quartz glass. However, in order to suppress the heat of the light source from being conducted to the grating portion, a support substrate having good heat dissipation characteristics can be used. In this case, alumina, aluminum nitride, silicon carbide, Si and the like can be exemplified.

The support substrate and the optical waveguide may be bonded via a bonding layer, or may be bonded directly at room temperature. In the case of direct bonding, the support substrate functions as a cladding part. In this case, it is preferable to provide a cladding layer having a refractive index smaller than that of the optical waveguide between the support substrate and the optical waveguide. The bonding surface becomes an amorphous layer, which scatters light and increases propagation loss. After forming a low-refractive-index cladding layer under the optical waveguide, this low-refractive-index cladding layer and support substrate are bonded directly. It is preferable to become a surface.

When the support substrate and the optical waveguide are bonded, the thickness of the bonding layer is not particularly limited, but is preferably 0.1 μm or more in order to ensure the adhesive strength for polishing the optical waveguide with a thin plate. More preferably, the thickness is 5 μm or more. In order to reduce the stress of the bonding layer, the thickness is preferably 3 μm or less, and more preferably 1.5 μm or less.

Further, a bonding layer functioning as a cladding layer may be provided between the support substrate and the optical waveguide, or a cladding layer in contact with the optical waveguide may be further provided in addition to the bonding layer.

In a preferred embodiment, a reflective film that reflects light emitted from the optical waveguide is provided between the optical waveguide and the support substrate. Thereby, the light quantity of the emitted light radiated | emitted out of an element can be made high. Such a reflective film may be a metal film such as gold, aluminum, copper, silver, or a dielectric film. When the reflective film is a metal film, the metal film is provided between the support substrate and the lower clad, and light propagating through the optical waveguide can be prevented from being absorbed by the metal film.

When a metal film is used as the reflective film, a metal layer such as Cr, Ni, or Ti can be formed as a buffer layer of the metal film so that the clad layer formed thereon is not peeled off. The material of the dielectric film is a single layer film or a multilayer film made of TiO ₂ , Si ₃ N ₄ , Ta ₂ O ₅ , SiO ₂ , MgF, CaF, or the like.

The ridge-type optical waveguide is obtained by, for example, physical processing and molding by cutting with an outer peripheral blade or laser ablation processing. Alternatively, the ridge type optical waveguide can also be formed by dry etching.

The material of the lower clad layer and the upper clad layer may be a material having a refractive index smaller than that of the single crystal constituting the optical waveguide, and may be an adhesive layer. The upper cladding may be air. Examples of the material of each cladding layer include silicon oxide, magnesium fluoride, calcium fluoride, silicon nitride, alumina, and tantalum pentoxide.

As the light source, a semiconductor laser composed of a mixed crystal material mainly composed of GaN, GaAs, and InP is suitable. A light source such as a laser array arranged in a one-dimensional manner can also be realized. It may be a super luminescence diode, LED, or semiconductor optical amplifier (SOA).
In the case of a light source including multiple wavelengths such as the above super luminescence diode or LED, the angle diffracted by the diffraction grating differs depending on the wavelength, so that it is possible to obtain diffuse light with a wider angle and no omission, so spatial resolution It is possible to collect three-dimensional data of the surface to be measured having a high height.

The Bragg grating can be formed by physical or chemical etching.
As a specific example, a metal film such as Ni or Ti is formed on a high refractive index substrate, and windows are periodically formed by photolithography using electron beam exposure or stepper exposure to form an etching mask. Thereafter, periodic grating grooves are formed by a dry etching apparatus such as reactive ion etching. Finally, it can be formed by removing the metal mask.

The period of the grating can be appropriately determined depending on the wavelength of the propagating light and the target radiation angle. In a preferred embodiment, when the wavelength of propagating light is 800 nm and 1 μm, the period of the periodic grating portion can be changed in a range of 0.1 to 2 μm, so that the radiation angle is in the range of +90 to −90 °. It can be adjusted as appropriate.
Note that the radiation angle is θa shown in FIG. 4, and the radiation angle on the emission side is positive with respect to the normal direction P of the optical waveguide.

The above is the case where the diffraction order is the first order, but higher-order diffracted light can be used as described above. FIG. 6 shows the calculated values of the grating period and the radiation angle in the diffracted light from the first order to the fourth order. From FIG. 6, the radiation angle can be changed by using second-order or higher-order diffracted light as compared to the case where the first-order diffracted light is used. Further, even if the grating period is increased, the same radiation angle as that obtained when the first-order diffracted light is used can be obtained. Thus, in the grating patterning process, patterning can be performed with the mask aligner without using an expensive apparatus such as a stepper or an electron beam exposure machine, and an inexpensive optical scanner element can be realized.

Here, each grating part can use second-order diffracted light, third-order diffracted light, and fourth-order diffracted light in addition to the first-order diffracted light, and in principle, by adding each radiated light, the hemisphere of the grating forming surface It is possible to radiate the surface.
In this case, by setting the wavelength of the incident light source to multiple wavelengths and a broad wavelength, the radiation angle from each diffraction grating can be widened, so that light can be diffused at a wider angle.

Furthermore, a wide range of radiation angles can be realized by using a combination of multiple types of diffracted light with different orders. For example, as illustrated in FIG. 7, only by forming a grating portion having a grating period of 1 μm to 2 μm, + 90 ° to + 60 ° is a first-order diffracted light, + 60 ° to + 30 ° is a second-order diffracted light, and + 30 ° to 0 ° is By making the third-order diffracted light from 0 ° to -90 ° into the fourth-order diffracted light, it is possible to construct a wide-angle variable detection light generating element with a small number of grating parts, and it is possible to reduce the size, increase the angular resolution, and reduce the cost. It can be realized.

The surface to be measured can be scanned using the detection light generating element of the present invention. That is, it is possible to irradiate the surface to be measured with the emitted light emitted from the detection light generating element, and obtain data on the surface to be measured using the reflected light from the surface to be measured. Such data includes the position of the surface to be measured.

In a preferred embodiment, the surface to be measured is scanned while moving the detection light generating element in the longitudinal direction of the detection light generating element. This embodiment will be further described.

As shown in FIG. 4, the divergence angle of the light emitted from the element is narrow in the waveguide propagation direction (longitudinal direction of the element) L, in a direction W parallel to the grating surface and parallel to the upper surface 6c of the optical waveguide. It becomes wider toward you. When viewed in the longitudinal direction of the element, emitted light is radiated from each grating portion at a different radiation angle θa.

For this reason, when used as a three-dimensional laser scanner for automatic driving of an automobile, scanning in the vertical direction can be eliminated by aligning the longitudinal direction L of the element with the horizontal direction and the direction W with the vertical direction. The number of elements can be reduced, and an inexpensive device configuration can be obtained.

For example, the system shown in FIG. 8 shows a light receiving element division method.
Light emitted from the semiconductor laser 41 is collected by the lens 22 and projected onto the measurement surface 23. Then, the reflected light from the surface to be measured is projected onto the light receiving element array 25 by the lens 24. Here, the light receiving element array 25 includes a plurality of photodiodes arranged in the horizontal direction X and the vertical direction Y in order to detect information on the surface to be measured with high resolution. In this method, since a high-precision mirror such as a polygon mirror and a MEMS mirror and an optical scanning element using a plurality of lasers are not used, a relatively inexpensive system can be obtained. The light receiving element array can be lower in cost than a system using an optical scanning element or a plurality of lasers. However, it is necessary to install a large number of photodiodes in each of the horizontal direction X and the vertical direction Y of the surface to be measured. In addition, since the emitted light is projected from one element, there is a demerit that the light intensity corresponding to each light receiving element is low and the signal / noise ratio is low.

FIG. 9 shows an optical scanning system using a laser scanner.
In this example, the laser element 21 </ b> A is scanned in the X and Y directions by the polygon mirror, and the light is condensed by the lens 22 to irradiate the measurement surface 23. Here, the surface to be measured 23 is sequentially scanned in the X direction and the Y direction. Then, the reflected light from the surface to be measured is collected by the lens 24 and received by the light receiving element 25A. However, this method requires a mechanism that scans both the X direction and the Y direction with laser light.

In FIG. 10, the detection light generating elements 1 and 1A of the present invention are used. Here, the emitted light from the element of the present invention has a property of spreading in a direction W perpendicular to the longitudinal direction L of the element. For this reason, when the longitudinal direction L of the element coincides with the horizontal direction X, the light emitted from the element spreads in the horizontal direction X and the vertical direction Y, respectively. When the emitted light is projected onto the measurement surface 23 through the lens 22, it is projected toward the region 23 a extending in the vertical direction on the measurement surface 23. The reflected light from this region 23a is collected by the lens 24 and received by the light receiving element array 25B.

Since the beam generated from the detection light generating element of the present invention spreads in a wide angle in the Y direction, as shown in FIG. 11, a lens 22 for condensing the emitted light from the detection light generating element 1 (1A) is provided. Without scanning, it is possible to scan the surface to be measured.

Here, when the element of the present invention is used, the emitted light can be projected on the entire surface to be measured, and the reflected light can be measured by the two-dimensional light receiving element array 25B. Therefore, the entire surface to be measured can be irradiated at once without moving the elements 1 and 1A in the longitudinal direction L of the element, and information on the entire surface to be measured can be obtained. As a result, the time and cost required for scanning can be reduced as compared with the conventional case, and the cost of the light receiving element array can be significantly reduced. However, the two-dimensionally arranged light receiving element array may be a photodiode, a CMOS camera, or a CCD.

A supplementary description will be given of a distance measuring method using a semiconductor laser.
In this method, the distance to the obstacle is measured by irradiating a laser beam, detecting the reflected light from the obstacle with a light receiving element, and measuring the propagation time after irradiation. Generally, it is called a time off flight (TOF) method.

When performing distance measurement in a three-dimensional space using the element of the present invention, the divergence angle of light emitted from the element depends on the waveguide shape and the waveguide width W direction depending on the waveguide core and cladding material selection. Can be enlarged from 5 ° to 40 °, and the whole can be irradiated with a radiation angle of 180 ° in principle in the longitudinal direction L of the element. By utilizing this characteristic, it is possible to construct a distance measuring system using a two-dimensional photodiode array in the horizontal direction X and the vertical direction Y as shown in FIGS. As a result, the measurement distance equivalent to that of the conventional split type light receiving method can be increased, and at the same time, a low-cost system can be realized.

Since the beam generated from the detection light generating element of the present invention spreads in a wide angle in the Y direction, as shown in FIG. 11, a lens 22 for condensing the emitted light from the detection light generating element 1 (1A) is provided. Without scanning, it is possible to scan the surface to be measured.

In a preferred embodiment, an optical material layer 14 is formed on the support substrate 2 via the lower buffer layer 3 as shown in FIG. For example, a pair of ridge grooves 30 are formed in the optical material layer 14, and the ridge type optical waveguide 6 is formed between the ridge grooves. The grating portion can be provided on the support substrate side of the optical waveguide, or can be provided on the opposite side of the support substrate. 31 is a thin part, 32 is an extension part. In this example, there is no upper clad layer, and the optical material layer 14 faces the air. An adhesive layer may be provided between the clad layer 3 and the support substrate 2.

In the element shown in FIG. 12B, an upper cladding layer 50 is further formed on the optical material layer 14.

Further, as shown in FIG. 12C, an optical material layer 14 is formed on the support substrate 2 via the lower clad layer 3. For example, a pair of ridge grooves 30 are formed in the optical material layer 14, and the ridge type optical waveguide 6 is formed between the ridge grooves. In this example, a ridge groove is provided on the support substrate side. 31 is a thin part, 32 is an extension part.

In a preferred embodiment, the optical waveguide is composed of a core made of an optical material, and a clad surrounds the core. The cross section of the core (cross section in the direction perpendicular to the light propagation direction) is a convex figure.

The convex figure means that a line segment connecting any two points of the outer contour line of the core cross section is located inside the outer contour line of the core cross section. A convex figure is a general geometric term. Examples of such figures include triangles, quadrangles, hexagons, octagons, and other polygons, circles, ellipses, and the like. As the quadrangle, a quadrangle having an upper side, a lower side, and a pair of side surfaces is particularly preferable, and a trapezoid is particularly preferable.

For example, as shown in FIG. 13A, an optical waveguide core 37 is formed on the support substrate 2 via the lower clad layer 3. The cross-sectional shape of the core 37 is a trapezoid, and the upper surface 37a is narrower than the lower surface 37b. A clad layer 36 is formed so as to cover the core 37. An adhesive layer can also be formed between the cladding layer 36 and the support substrate 2.

In the element shown in FIG. 13B, a clad layer 39 is provided on the support substrate 2, and an optical waveguide core 37 is embedded in the clad layer 39. The clad layer 39 has an upper surface covering portion 39b covering the upper surface of the optical waveguide core, a side surface covering portion 39c covering the side surface of the optical waveguide, and a bottom surface covering portion 39a positioned between the optical waveguide and the support substrate.

In the element shown in FIG. 13C, a clad layer 39 is provided on the support substrate 2, and an optical waveguide core 37 A is embedded in the clad layer 39. The clad layer 39 has an upper surface covering portion 39b covering the upper surface of the optical waveguide core, a side surface covering portion 39c covering the side surface of the core, and a bottom surface covering portion 39a between the core and the support substrate.

Further, in the element shown in FIG. 14A, an optical waveguide core 37 is formed on the support substrate 2 via the lower clad layer 3. An upper cladding layer 36 is formed on the side surface and the upper surface 37 a of the optical waveguide core 37 to cover the optical waveguide core 37. The upper clad layer 36 has a side surface coating portion 36 b that covers the side surface of the optical waveguide core 37 and an upper surface coating portion 36 a that covers the upper surface.

In the element shown in FIG. 14B, an optical waveguide core 37A is formed. The cross-sectional shape of the optical waveguide 37A is trapezoidal, and the lower surface is narrower than the upper surface. The upper clad layer 36 includes a side surface coating portion 36b that covers the side surface of the optical waveguide core 37A and an upper surface coating portion 36a that covers the upper surface.

(Experiment 1)
A detection light generating element 1A as shown in FIGS. 2, 3, and 12B was produced.
Specifically, an optical material layer 14 was formed on a support substrate 2 made of quartz by a sputtering apparatus to form 0.5 μm of SiO 2 as a cladding layer and 2 μm of Ta 2 O 5 thereon. Next, Ti was formed on the optical material layer 14, and a grating pattern was produced by a photolithography technique using electron beam exposure. Thereafter, nine grating portions were formed by fluorine-based reactive ion etching using the Ti pattern as a mask. The groove depth of the grating part was 300 μm, the length of each grating part was 100 μm, and nine grating periods were formed at intervals of 0.1 μm from 1.2 μm to 2 μm.

Next, in order to form the optical waveguide 6, grooves having a width of 3 μm and a depth of 1 μm were performed by reactive ion etching in the same manner as described above.

After fixing a semiconductor laser having a wavelength of 900 nm on a silicon substrate with AuSn solder, the detection light generating element chip is aligned with the optical axis of the laser light to be aligned with the optical axis of the optical waveguide, and fixed to the AuSn solder. A laser module was produced.

After mounting, the laser was driven, the light was propagated through the optical waveguide 6, and the radiation angle of the value diffracted light emitted from each grating portion was measured.
As a result, the following diffracted light was emitted when the grating portions having the short cycle were sequentially set to 16A, 16B, 16C, 16D, 16E, 16F, 16G, 16H, and 16I.

Grating part Diffracted light Radiation angle 16B First order diffracted light 80 °
16A First order diffracted light 71 °
16I Second order diffracted light 57.5 °
16H Second order diffracted light 54.2 °
16G Second order diffracted light 50 °
16F Second order diffracted light 47 °
16E Second order diffracted light 43.6 °
16D Second order diffracted light 39.7 °
16C Second order diffracted light 35.5 °
16B Second order diffracted light 31 °
16H 3rd order diffracted light 29.3 °
16G 3rd order diffracted light 25.8 °
16F Third-order diffracted light 22 °
16E Third-order diffracted light 18 °
16D Third-order diffracted light 13.3 °
16C Third-order diffracted light 8.2 °
16B Third order diffracted light 2.5 °
16F 4th order diffracted light 0.8 °
16E 4th order diffracted light -4.3 °
16D 4th order diffracted light -10.2 °
16C 4th order diffracted light -17 °
16B 4th order diffracted light -25.3 °
16A 4th order diffracted light -35.8 °

As a result, it was confirmed that light can be emitted in an angle range of + 80 ° to −35 °. Further, it has been demonstrated that light is extracted to the outside of the waveguide in a wide angle region of 40 ° in the width direction of the optical waveguide and 115 ° in the longitudinal direction of the device with respect to the spread angle of the laser light emitted to the outside of the device.

Claims (8)

A detection light generating element for irradiating the measurement surface with detection light,
Optical waveguide,
A grating portion formed of grooves and protrusions periodically formed in the optical waveguide, and a cladding portion that is in contact with the optical waveguide and made of a material having a refractive index lower than that of the material of the optical waveguide,
A detection light generating element characterized in that propagating light propagating through the optical waveguide is diffracted by the grating section, and diffracted light generated from the grating section is emitted in a plurality of directions as the detection light. 2. The element according to claim 1, comprising a plurality of the grating portions, wherein the plurality of grating portions have different periods. 3. The element according to claim 1, wherein the diffracted light is first-order diffracted light. 3. The element according to claim 1, wherein the diffracted light is high-order diffracted light. 3. The element according to claim 1, wherein a plurality of different orders of diffracted light are emitted as the diffracted light. The element according to any one of claims 1 to 5, wherein the optical waveguide is a ridge-type optical waveguide. A method of irradiating the surface to be measured with the detection light using the detection light generating element according to any one of claims 1 to 6,
A method for irradiating detection light, wherein the detection light emitted from the detection light generation element is irradiated onto the surface to be measured, and data relating to the surface to be measured is obtained using reflected light from the surface to be measured. The method according to claim 7, wherein the surface to be measured is scanned while moving the detection light generation element in a longitudinal direction of the detection light generation element.

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